The present invention is related to an apparatus for removing a welding bulge, and in particular, to an apparatus for removing a welding bulge from resistance welded pipes while laying pipelines.
Variously constructed and modified apparatus for removing a welding bulge, intended for operation in specific conditions, are well known in the art.
The invention is directed to an apparatus designed for field operation while laying pipelines for the long-distance transporation of petroleum and gas. More specifically, the present invention deals with the apparatus designed for removing a welding bulge from resistance welded pipes under the aforesaid conditions.
Apparatus thus far proposed, as exemplified in USSR Inventor's Certificate Nos. 507373, 468729, 468730, generally comprise impact or cutting tools, motion and static parts, and mechanisms for driving the tools.
Such apparatus, particularly those intended for large-diameter (over 1,000 mm) pipes, are of large dimensions and heavy weight, and therefore present problems in service and are greatly time-consuming for setup under field conditions in pipeline construction. As a consequence, their performance has proved to be lower than that of the electric resistance welding machines, which machines together with the apparatus in question forming part of a single production complex.
Known in the prior art is an apparatus for removing a welding bulge from resistance welded pipes as disclosed in USSR Inventor's Certificate No. 589090. This apparatus comprises a U-shaped carrier adapted to be placed at the bulge zone in spaced circumferential relationship to the welded pipes and it is provided with centering rollers, at least two of which are radially movable with respect to the center of the welded pipes circumference and are generally disposed on the end portions of the carrier, and cutting tool holders disposed on the carrier provide movement to and from the weld bulge.
The radially movable centering rollers are motor-operated, whereby the carrier will be turned about the pipes at the weld bulge zone.
In operation, the motor-operated centering rollers by rolling over the pipes impart rotary motion to the carrier. As this takes place, the holders will perform the approach of the cutting tools to the weld bulge and the carrier will provide the feed of this tool.
Though simple in construction, this apparatus will suffers from a number of disadvantages.
Inasmuch as the motor-operated centering rollers of the known apparatus are supported upon the welded pipes, the reliability of the drive for feeding cutting tools is completely dependent on the engagement of the motor-operated rollers with the surface of the pipe, providing the drive power is sufficient to defeat resistance to the cutting tools.
The reliability of the roller-pipe engagement is in turn dependent on the surface condition of the pipes and the rollers, since under field conditions there may be ice formation, oil film, and other friction-affecting deposition formations which can affect the friction between the contacting parts. This brings about vibration in the tools and a drop in the speed of feeding thereof, which in turn impairs performance of the prior art apparatus. The problem of performance is even more acute in view of the fact that the welding bulge has to be removed in more than one pass.